1. Field of the invention
This invention relates, in general, to air conditioning systems. In particular, the invention relates to a system in which a conditioned air is simultaneously supplied to a plurality of rooms to be air-conditioned from one air conditioning apparatus through a duct.
2. Description of the related art
A conventional central air conditioning system typically includes one air conditioning source and a duct which communicates with a plurality of rooms to be air-conditioned through corresponding paths to simultaneously control the temperature in the rooms. The conventional air conditioning system usually is provided with an automatic air volume control function, i.e., a so-called VAV (variable air volume) unit. In VAV unit, a damper and an air volume sensor are arranged in the path formed between the duct and each room, and the opening degree of each damper is controlled on the basis of the heat load of the corresponding rooms. In other words, the volume of the conditioned air fed from the air conditioning source to each room is determined based on the difference between a desired room temperature set by the thermostat provided in each room and a detected room temperature (actual room temperature).
In the above-described conventional air conditioning system including the VAV unit, the temperature of the conditioned air fed from the air conditioning source is previously set at a desirable level through the operation panel or the remote controller of the air conditioning source, and the temperature of each room is controlled by each damper which varies the volume of the conditioned air fed to each room. During the operation, the capacity of the compressor of the air conditioning source is controlled to maintain the temperature of the conditioned air fed from the air conditioning source at a set level. The total flow rate of the conditioned air is controlled by the fan device. Furthermore, in this system, a minimum volume of air fed to each room is set to secure a suitable volume of air ventilating each room, and the volume of air fed into each room is controlled such that it is not reduced below the minimum volume of air. In other words, a damper is not fully closed even though further supplying of the conditioned air in the corresponding room is not required. Thus some conditioned air is always supplied into the room until the air conditioning source stops. Thus, if the heat load in each room is smaller than the heating/cooling capacity of the air conditioning source corresponding to the previously set temperature of the conditioned air fed from the air conditioning source, each room may be heated or cooled in excess as long as the air conditioning source is operating even though each damper is at the closed position and the capacity of the fan device is at the minimum value. When the heat load in each room becomes greater than the heating/cooling capacity of the air conditioning source, the temperature of each room may not reach the desired temperature set by the thermostat even though each damper is fully opened and the capacity of the fan device is at the maximum level.